Bend alignment type liquid crystal display apparatus

ABSTRACT

A liquid crystal display apparatus includes a liquid crystal layer sealed between a first substrate and a second substrate opposed to each other. Inner surfaces of the first and second substrates have been subjected to aligning treatment to splay-align liquid crystal molecules. The liquid crystal display further includes electrodes formed on the inner surfaces of the first and second substrates to generate an alignment transition electric field to cause the liquid crystal molecules to transit from splay alignment to bend alignment. The alignment transition electric field includes a vertical electric field in the thickness direction of the liquid crystal layer, and a horizontal electric field in a direction parallel to the inner surfaces of the first and second substrates to twist the liquid crystal molecules between the substrates.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional of U.S. application Ser. No. 11/689,938, filed Mar.22, 2007 now U.S. Pat. No. 8,009,254, which is based upon and claims thebenefit of priority from prior Japanese Patent Application No.2006-091290, filed Mar. 29, 2006, the entire contents of both of whichare incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a bend alignment type liquid crystaldisplay apparatus.

2. Description of the Related Art

A bend alignment type liquid crystal display apparatus includes a liquidcrystal layer in which liquid crystal molecules have a splay alignmentin an initial alignment state. After transition from the splay alignmentto bend alignment of the liquid crystal molecules, the alignment stateof the liquid crystal molecules in the bend alignment is controlled.

The bend alignment type liquid crystal display apparatus includes aliquid crystal layer sealed in a gap between a pair of substratesopposed to each other. Inner surfaces of the substrates have beensubjected to aligning treatment to align the liquid crystal molecules ofthe liquid crystal layer in a splay configuration. The liquid crystalmolecules of the liquid crystal layer have a splay alignment in whichthe major axes of the molecules align in the direction of aligningtreatment. The inner surfaces of the substrates are provided withopposing electrodes. Between the electrodes, an electric field to causethe liquid crystal molecules to transit from the splay alignment to thebend alignment is applied at the start, and a driving electric fieldcorresponding to image data is applied after the start.

At the start, in the bend alignment type liquid crystal displayapparatus, an electric field which causes the alignment transition isgenerated between the electrodes of the substrates to transit thealignment of the liquid crystal molecules from the splay alignment tothe bend alignment. After that, a driving electric field correspondingto the image data is generated between the electrodes to control thealignment state of the liquid crystal molecules in the bend alignment,thus displaying an image.

In the bend alignment type liquid crystal display apparatus, to causethe liquid crystal molecules to transit from the splay alignment at thestart to the bend alignment within a short period of time at a lowvoltage is sought for.

For this purpose, conventionally, to use a liquid crystal materialhaving a small ratio K₃₃/K₁₁ of a splay elastic constant K₁₁ to a bendelastic constant K₃₃ (see Jpn. Pat. Appln. KOKAI Publication No.8-87013) and to subject the inner surface of at least one of thesubstrates to treatment that changes the rising state of the liquidcrystal molecules among regions upon application of an alignmenttransition voltage (see Jpn. Pat. Appln. KOKAI Publication No.2000-66208) have been proposed.

BRIEF SUMMARY OF THE INVENTION

A liquid crystal display apparatus according to an aspect of the presentinvention includes a liquid crystal layer sealed between a firstsubstrate and a second substrate opposed to each other, wherein liquidcrystal molecules of the liquid crystal layer are nematic liquidcrystals having positive dielectric anisotropy. Inner surfaces of thefirst and second substrates have been subjected to aligning treatment toalign the liquid crystal molecules in a splay configuration. The liquidcrystal display further includes electrodes formed on the inner surfacesof the first and second substrates to generate an alignment transitionelectric field to cause the liquid crystal molecules to transit fromsplay alignment to bend alignment. The alignment transition electricfield comprises a vertical electric field in a thickness direction ofthe liquid crystal layer, and a horizontal electric field in a directionparallel to the inner surfaces of the first and second substrates totwist the liquid crystal molecules between the substrates.

Additional objects and advantages of the invention will be set forth inthe description which follows, and in part will be obvious from thedescription, or may be learned by practice of the invention. The objectsand advantages of the invention may be realized and obtained by means ofthe instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The accompanying drawings, which are incorporated in and constitute apart of the specification, illustrate embodiments of the invention, andtogether with the general description given above and the detaileddescription of the embodiments given below, serve to explain theprinciples of the invention.

FIG. 1 schematically shows the arrangement of a liquid crystal displayapparatus according to an embodiment of the present invention;

FIG. 2 is a sectional view of part of the liquid crystal displayapparatus according to the embodiment of the present invention;

FIG. 3 is a plan view of part of a substrate of the liquid crystaldisplay apparatus;

FIG. 4 shows the aligning treatment directions of inner surfaces of apair of substrates and directions of the transmission axes of a pair ofpolarization plates in the liquid crystal display apparatus;

FIG. 5A is an alignment state view, in an initial alignment state, ofliquid crystal molecules on a section parallel to the aligning treatmentdirection;

FIG. 5B is an alignment state view, in the initial alignment state, ofthe liquid crystal molecules on a section parallel to a directionperpendicular to the aligning treatment direction;

FIG. 6A is an alignment state view, in an alignment transition process,of the liquid crystal molecules on the section parallel to the aligningtreatment direction;

FIG. 6B is an alignment state view, in the alignment transition process,of the liquid crystal molecules on the section parallel to the directionperpendicular to the aligning treatment direction;

FIG. 7A is an alignment state view, after the alignment transition, ofthe liquid crystal molecules on the section parallel to the aligningtreatment direction; and

FIG. 7B is an alignment state view, after the alignment transition, ofthe liquid crystal molecules on the section parallel to the directionperpendicular to the aligning treatment direction.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 to 4, 5A, 5B, 6A, 7A, and 7B show an embodiment of the presentinvention. FIG. 1 schematically shows the schematic arrangement of aliquid crystal display apparatus according to the embodiment of thepresent invention, FIG. 2 is a sectional view of part of the liquidcrystal display apparatus, and FIG. 3 is a plan view of part of asubstrate of the liquid crystal display apparatus. FIG. 4 shows thedirections of aligning treatment done on inner surfaces of a pair ofsubstrates and directions of the transmission axes of a pair ofpolarization plates in the liquid crystal display apparatus. FIGS. 5A,5B, 6A, 6B, 7A, and 7B are schematic views each showing a change inalignment state of the liquid crystal molecules between the substrates.

As shown in FIGS. 1 to 3, this liquid crystal display apparatus includesa liquid crystal display device 100 and a display driver 200 to drivethe liquid crystal display device 100.

The liquid crystal display device 100 includes a pair of transparentsubstrates, e.g., first and second substrates 1 and 2, a liquid crystallayer 3, transparent first and second electrodes 4 and 5, a transparentthird electrode 15, alignment films 17 and 18, and a pair ofpolarization plates 19 and 20. The first and second substrates 1 and 2are opposed to each other via a gap and bonded to each other through aframe-like seal member (not shown). The liquid crystal layer 3 is sealedin a region between the substrates 1 and 2 and surrounded by theframe-like seal member. The first and second electrodes 4 and 5 areformed on one of the inner surfaces of the substrates 1 and 2, e.g., theinner surface of the first substrate 1. The third electrode 15 is formedon the inner surface of the remaining one of the substrates 1 and 2,e.g., the inner surface of the second substrate 2. The alignment films17 and 18 are formed on the inner surfaces of the substrates 1 and 2 andare subjected to aligning treatment to align liquid crystal molecules 3a of the liquid crystal layer 3 in a splay configuration. Thepolarization plates 19 and 20 are arranged to sandwich the substrates 1and 2. The liquid crystal layer 3 comprises nematic liquid crystalshaving positive dielectric anisotropy.

At the start of the liquid crystal display apparatus, the first to thirdelectrodes 4, 5, and 15 of the liquid crystal display device 100generate an alignment transition electric field. The alignmenttransition electric field comprises a vertical electric field (anelectric field in a direction substantially parallel to the directionsof normal to the first and second substrates) with a predetermined valueand a horizontal electric field (an electric field which intersects thevertical electric field and extends in a direction substantiallyparallel to the substrates surfaces, i.e., the inner surfaces, of thesubstrates 1 and 2). The vertical electric field serves to cause theliquid crystal layer sealed between the substrates to transit from thesplay alignment in an initial state to bend alignment. The horizontalelectric field serves to twist the liquid crystal molecules 3 a. In thiscase, the first electrodes 4 serve as auxiliary electrodes to generatethe horizontal electric field. After the start of the liquid crystaldisplay apparatus, the second electrodes 5 serve as pixel electrodes andthe third electrode 15 serves as a counterelectrode, to generate adriving electric field corresponding to the image data in the thicknessdirection of the liquid crystal layer 3.

At the start of the liquid crystal display apparatus, the display driver200 supplies a voltage to generate the alignment transition electricfield to the respective electrodes of the liquid crystal display device100. After the start of the liquid crystal display apparatus, thedisplay driver 200 supplies a voltage to generate an electric fieldcorresponding to the image data in the thickness direction of the liquidcrystal layer to at least the second electrodes 5 and third electrode15.

This liquid crystal display apparatus has pixels 110 which controltransmission of light to form one display element. The pixels 110 arearranged in row directions and column directions to form a matrix. Thefirst and second electrodes 4 and 5 are formed on the inner surface ofone of the substrates 1 and 2, e.g., the substrate 1 (to be referred toas the rear substrate hereinafter) on a side opposite to the displayobservation side (upper side in FIG. 1). The first and second electrodes4 and 5 are insulated from each other and correspond to the pixels 110.The third electrode 15 is formed on the inner surface of the remainingone of the substrates 1 and 2, e.g., the substrate 2 (to be referred toas the front substrate hereinafter) on an observation side,corresponding to the pixels 110.

The first electrodes 4 are formed to correspond to at least the entirerange of the pixels 110. The second electrodes 5 are formed on aninterlayer dielectric film 14, which covers the first electrodes 4, intoshapes each having an area smaller than an area of each pixel 110. Thesecond electrodes 5 respectively oppose the first electrodes 4 at theiredges.

The liquid crystal display apparatus is an active matrix displayapparatus, which selects and drives the pixels 110 arranged in thematrix by an active device comprising TFTs (Thin Film Transistors) 6.The first electrodes 4 are arranged for each row to correspond to thepixels 110 of the row. The second electrodes 5 are arranged tocorrespond to the pixels 110 and connected to the TFTs 6 formed on theinner surface of the rear substrate 1.

Each TFT 6 has a gate electrode 7, a gate insulating film 8, an i-typesemiconductor film 9, source electrode 10, and a drain electrode 11. Thegate electrode 7 is formed on a substrate surface of the rear substrate1. The gate insulating film 8 is formed almost on the entire surface ofthe rear substrate 1 to cover the gate electrode 7. The i-typesemiconductor film 9 is formed on the gate insulating film 8 to opposethe gate electrode 7. The source electrode 10 and drain electrode 11 areformed on the two side portions of the i-type semiconductor film 9through n-type semiconductor films (not shown).

The inner surface of the rear substrate 1 is provided with scanninglines 12 to supply gate signals to the TFTs 6 of the respective rows,and signal lines 13 to selectively supply a start signal and image datasignal (described later) to the TFTs 6 of the respective columns. Thescanning lines 12 are formed on the substrate surface of the rearsubstrate 1 to be integral with the gate electrodes 7 of the TFTs 6. Thesignal lines 13 are formed on the gate insulating film 8 and connectedto the drain electrodes 11 of the TFTs 6.

The first electrodes 4 comprise conductive films 4 a formed on the gateinsulating film 8 to correspond to the respective pixel rows. Theconductive films 4 a are connected to each other in common at theirends. A voltage to generate an electric field with a predeterminedstrength with respect to the second electrodes 5 is supplied to theconductive films 4 a.

According to this embodiment, the portions between those regions of theconductive films 4 a which correspond to the respective pixels 110 havesmall widths. Alternatively, the conductive films 4 a may have widths tocorrespond to the entire areas of the pixels 110 throughout sufficientlylarge ranges of their entire lengths.

The second electrodes 5 respectively comprise comb-shaped conductivefilms 5 a formed on the interlayer dielectric film 14, which covers thefirst electrodes 4, to correspond to the respective pixels 110. Eachcomb-shaped conductive film 5 a is patterned into a comb shape havingelectrode finger portions. The comb-shaped conductive film 5 a isconnected to the source electrode 10 of the corresponding TFT 6 at oneend of its base that joins the respective electrode finger portions.

The interlayer dielectric film 14 is formed almost on the entire surfaceof the rear substrate 1 to cover the first electrodes 4, TFTs 6, andsignal lines 13. Each comb-shaped conductive film 5 a is connected tothe source electrode 10 of the corresponding TFT 6 through a contacthole (not shown) formed in the interlayer dielectric film 14.

For example, each comb-shaped conductive film 5 a has four electrodefinger portions formed equidistantly. The electrode finger portions havethin, elongated shapes extending in a direction which is inclined withrespect to the vertical direction of the screen of the liquid crystaldisplay apparatus, i.e., a vertical axis 120 of the screen, at an angleθ of 5° to 15° in either the left or right direction.

The third electrode 15 on the inner surface of the front substrate 2comprises a conductive film opposing the entire arrangement region ofthe pixels 110. A predetermined countervoltage is supplied to one ormore portions of the peripheral portion of the third electrode 15.

This liquid crystal display apparatus is a color image display apparatushaving red, green, and blue color filters 16R, 16G, and 16B respectivelycorresponding to the pixels 110. The color filters 16R, 16G, and 16B areformed on a substrate surface of the front substrate 2, and the thirdelectrode 15 is formed on the color filters 16R, 16G, and 16B.

The inner surfaces of the substrates 1 and 2 are respectively providedwith homogeneous alignment films 17 and 18, which cover the first andsecond electrodes 4 and 5 and the third electrode 15, respectively. Thesplay aligning treatment of the liquid crystal molecules 3 a of theliquid crystal layer 3 is done by rubbing the film surfaces of thealignment films 17 and 18 in the same direction which obliquelyintersects the direction of lengths of the respective electrode fingerportions of the second electrodes 5 comprising the comb-shapedconductive films 5 a at a predetermined angle.

FIG. 4 shows aligning treatment directions 1 a and 2 a (the rubbingdirections of the alignment films 17 and 18) of the inner surfaces ofthe substrates 1 and 2 and the directions of transmission axes 19 a and20 a of the polarization plates 19 and 20 which are arranged to sandwichthe substrates 1 and 2.

As shown in FIG. 4, the aligning treatment directions 1 a and 2 a of theinner surfaces of the substrates 1 and 2 are of the same direction andparallel to each other in a direction which is inclined with respect tothe direction of lengths of the respective electrode finger portions ofthe second electrodes 5, in a direction opposite to the direction ofinclination of the electrode finger portions with respect to thevertical axis 120 of the screen, at the angle θ (θ=5° to 15°) which issubstantially the same as the angle of inclination of the electrodefinger portions with respect to the vertical axis 120, that is, adirection substantially parallel to the vertical axis 120 of the screen.With this aligning treatment, in the initial state, the liquid crystalmolecules 3 a of the liquid crystal layer 3 have a splay alignment inwhich the major axes of the molecules align in the aligning treatmentdirections 1 a and 2 a of the inner surfaces of the substrates 1 and 2.

One of the polarization plates 19 and 20, e.g., the rear polarizationplate 19, is arranged such that its transmission axis 19 a issubstantially parallel to the aligning treatment directions 1 a and 2 a.The remaining one of the polarization plates 19 and 20, e.g., the frontpolarization plate 20, is arranged such that its transmission axis 20 ais substantially perpendicular, or substantially parallel, to thetransmission axis 19 a of the rear polarization plate 19. In thisembodiment, the transmission axes 19 a and 20 a of the polarizationplates 19 and 20 are perpendicular to each other to constitute anormally black mode liquid crystal display apparatus.

This liquid crystal display apparatus also has a conductive film 21,arranged between the front substrate 2 and the polarization plate 20which is arranged on the outer surface of the substrate 2, to blockstatic electricity from the outside (observation side).

Between the second electrode 5 formed on the inner surface of the rearsubstrate 1 and the third electrode 15 formed on the inner surface ofthe front substrate 2, at the start of the liquid crystal displayapparatus, a vertical electric field with a predetermined value isgenerated in the thickness direction of the liquid crystal layer 3. Thevertical electric field causes the liquid crystal molecules 3 a totransit from the splay alignment to the bend alignment. After the start,a driving electric field corresponding to the image data is generated inthe thickness direction of the liquid crystal layer 3. Between the firstand second electrodes 4 and 5 formed on the inner surface of the rearsubstrate 1, at the start, a horizontal electric field is generated. Thehorizontal electric field aligns the liquid crystal molecules of anintermediate layer, excluding the liquid crystal molecules of the liquidcrystal layer which is adjacent to the substrate surfaces, i.e., theinner surfaces, of the substrates 1 and 2, with a twist in a planeparallel to the substrate surfaces. The horizontal electric fieldintersects the direction of the vertical electric field and issubstantially parallel to the substrate surfaces.

More specifically, in this liquid crystal display apparatus, at thestart, the display driver 200 supplies the start signal with thepredetermined voltage within the range of, e.g., 5 V to 10 V to thesecond electrodes 5 through the signal lines 13 and TFTs 6. The startsignal generates the vertical electric field with a strengthcorresponding to the start signal between the second and thirdelectrodes 5 and 15. At the same time, the display driver 200 supplies avoltage with a predetermined voltage to the first electrodes 4. Thisgenerates a horizontal electric field with a predetermined strengthbetween the second and first electrodes 5 and 4, more specifically,between the edges of the electrode finger portions of the secondelectrodes 5 and those portions of the first electrodes 4 whichcorrespond to portions between the finger electrode portions of thesecond electrodes 5. An alignment transition electric field comprisingthe vertical electric field and horizontal electric field causes theliquid crystal molecules 3 a of the liquid crystal layer 3 to transitfrom the splay alignment to the bend alignment. After that, an imagedata signal is supplied to the second electrodes 5 through the signallines 13 and TFTs 6. The image data signal generates a driving electricfield corresponding to the image data between the second electrodes 5and third electrode 15. This controls the alignment state of the liquidcrystal molecules 3 a in the bend alignment to display an image.

FIGS. 5A, 5B, 6A, 6B, 7A, and 7B are views each schematically showing achange in alignment of the liquid crystal molecules 3 a at the start.FIG. 5A shows the alignment state, in the initial alignment state, ofthe liquid crystal molecules on a section parallel to the aligningtreatment direction. FIG. 5B shows the alignment state, in the initialalignment state, of the liquid crystal molecules on a section parallelto a direction perpendicular to the aligning treatment direction. FIG.6A shows an alignment state, in an alignment transition process, of theliquid crystal molecules on the section parallel to the aligningtreatment direction. FIG. 6B shows an alignment state, in the alignmenttransition process, of the liquid crystal molecules on the sectionparallel to the direction perpendicular to the aligning treatmentdirection. FIG. 7A shows an alignment state, after the alignmenttransition, of the liquid crystal molecules on the section parallel tothe aligning treatment direction. FIG. 7B shows an alignment state,after the alignment transition, of the liquid crystal molecules on thesection parallel to the direction perpendicular to the aligningtreatment direction.

In this liquid crystal display apparatus, at the start, the verticalelectric field is applied between the second electrodes 5 and thirdelectrode 15, and the horizontal electric field is applied between thesecond electrodes 5 and first electrodes 4. The vertical electric fieldapplies to the liquid crystal molecules 3 a a force that raises theliquid crystal molecules 3 a from the substrate surfaces. At this time,the liquid crystal molecules adjacent to the inner surfaces of thesubstrates 1 and 2 maintain the aligning direction and pretilt angle bythe alignment regulating force of the alignment films 17 and 18. Theliquid crystal molecules located in the intermediate layer of the liquidcrystal layer are to rise from the substrate surfaces. Simultaneously,the horizontal electric field in the direction perpendicular to thealigning treatment directions 1 a and 2 a is applied. The horizontalelectric field applies to the liquid crystal molecules of theintermediate layer of the liquid crystal layer a force that twists theliquid crystal molecules in a direction intersecting the aligningtreatment direction. Hence, the liquid crystal molecules of theintermediate layer start to align with a twist with respect to theliquid crystal molecules adjacent to the inner surfaces of thesubstrates 1 and 2. When the alignment of the liquid crystal molecules 3a is twisted in this manner, the intermolecular force among the liquidcrystal molecules that are adjacent in the thickness direction of theliquid crystal layer 3 decreases. This allows the liquid crystalmolecules to move easily. Thus, the weak vertical electric field appliedbetween the second electrodes 5 and third electrode 15 allows the liquidcrystal molecules 3 a to change their alignment state easily inaccordance with the alignment transition electric field. As a result, abend alignment state is obtained in which the liquid crystal moleculesalign such that the rise angles with respect to the surfaces of thesubstrates 1 and 2 sequentially increase from the vicinities of thesubstrates 1 and 2 toward the center of the thickness of the liquidcrystal layer 3.

In this liquid crystal display apparatus, at the start, the displaydriver 200 applies the vertical electric field and horizontal electricfield to the liquid crystal layer 3. Thus, the liquid crystal molecules3 a of the liquid crystal layer 3 transit from the splay alignment stateshown in FIGS. 5A and 5B, to the state shown in FIGS. 6A and 6B in whichthe splay alignment state and the twist alignment mix, and then to thebend alignment state shown in FIGS. 7A and 7B in which the major axes ofthe molecules align in the aligning treatment directions 1 a and 2 a ofthe inner surfaces of the substrates 1 and 2.

More specifically, in this liquid crystal display apparatus, thealignment transition electric field comprising the vertical electricfield and horizontal electric field changes the alignment state of theliquid crystal molecules 3 a from the splay alignment at the start tothe bend alignment. Hence, according to this liquid crystal displayapparatus, the twist alignment of the liquid crystal molecules obtainedby the horizontal electric field decreases the intermolecular forceamong the liquid crystal molecules in the splay alignment state. Thus,the transition of the liquid crystal molecules 3 a from the splayalignment at the start to the bend alignment takes place within a shortperiod of time and with a low voltage.

In contrast to this, in a conventional bend alignment type liquidcrystal display apparatus, only a vertical electric field in thethickness direction of the liquid crystal layer is applied to the liquidcrystal layer in the splay alignment state between the opposingelectrodes. After that, the vertical electric field is removed, and theliquid crystal molecules change to the bend alignment due to naturalrelaxation. Thus, the conventional liquid crystal display apparatusrequires a strong vertical electric field, and a long period of time forthe alignment transition.

In this manner, a liquid crystal display apparatus according to thepresent invention comprises a liquid crystal layer sealed between afirst substrate and a second substrate opposed to each other, innersurfaces of the first and second substrates having been subjected toaligning treatment to align liquid crystal molecules in a splayconfiguration, and a plurality of electrodes formed on the innersurfaces of the first and second substrates to generate an alignmenttransition electric field to cause the liquid crystal molecules totransit from splay alignment to bend alignment. The alignment transitionelectric field comprises a vertical electric field in a thicknessdirection of the liquid crystal layer, and a horizontal electric fieldin a direction parallel to the inner surfaces of the first and secondsubstrates to twist the liquid crystal molecules between the substrates.

In this liquid crystal display apparatus, preferably, the plurality ofelectrodes comprise first and second electrodes formed on the innersurface of the first substrate to be insulated from each other, and athird electrode formed in the inner surface of the second substrate. Theelectrodes preferably comprise first and second electrodes formed on theinner surface of the first substrate to be insulated from each other togenerate a horizontal electric field in a direction substantiallyparallel to the inner surface of the first substrate, and a thirdelectrode formed on the inner surface of the second substrate togenerate a vertical electric field in the thickness direction of theliquid crystal layer with respect to at least one of the first andsecond electrodes. In this case, preferably, each first electrodecomprises a conductive film with an area corresponding to a pixel toform one display element of the liquid crystal element apparatus, andeach second electrode comprises a transparent electrode, formed tooverlap the first electrode through an insulating film and including anarea smaller than an area of the first electrode, to generate thehorizontal electric field between the first electrode and an edge of thesecond electrode which overlaps the first electrode. Furthermore, eachsecond electrode desirably comprises a comb-shaped conductive filmformed on the first substrate and patterned into a comb shape includinga plurality of electrode finger portions extending in one direction.Preferably, the electrode finger portions of the comb-shaped conductivefilm extend in a direction intersecting the direction of aligningtreatment of the liquid crystal display apparatus.

Preferably, the liquid crystal display apparatus further comprises adisplay driver to supply a voltage to generate the alignment transitionelectric field to the plurality of electrodes when starting the liquidcrystal display apparatus, and a voltage to generate an electric fieldcorresponding to image data in the thickness direction of the liquidcrystal layer to at least two of the electrodes after the liquid crystaldisplay apparatus is started. Desirably, the plurality of electrodescomprise first and second electrodes formed on the inner surface of thefirst substrate to be insulated from each other, and a third electrodeformed on the inner surface of the second substrate, and the displaydriver supplies a voltage to generate the vertical electric field to atleast the second and third electrodes, and a voltage to generate thehorizontal electric field to the first and second electrodes.

A liquid crystal display apparatus according to the present inventioncomprise first and second substrates arranged to oppose each other at apredetermined gap, first electrodes formed on the inner surface of thefirst substrate, second electrodes, formed on the inner surface of thefirst substrate to be insulated from the first electrodes, to generate ahorizontal electric field in a predetermined first directionsubstantially parallel to the inner surfaces of the first and secondsubstrates with respect to the first electrodes, a first alignment filmwhich is formed on the inner surface of the first substrate to cover thefirst and second electrodes and which has been subjected to aligningtreatment in a second direction intersecting the first direction of thehorizontal electric field, a third electrode, formed on the innersurface of the second substrate to oppose the first and secondelectrodes, to generate a vertical field, at least with respect to thesecond electrodes, in a thickness direction of the gap between the firstand second substrates, a second alignment film which is formed on theinner surface of the second substrate to cover the third electrode andwhich has been subjected to aligning treatment in a direction which isparallel to the second direction of the first alignment film and thesame as the direction of the aligning treatment of the first alignmentfilm, a liquid crystal layer sealed in the gap between the first andsecond substrates and including liquid crystal molecules aligned in asplay configuration in accordance with alignment regulating forces ofthe first and second alignment films, and a pair of polarization platesprovided respectively outside the first and second substrates.

In this liquid crystal display apparatus, preferably, each firstelectrode comprises a transparent conductive film with an areacorresponding to a pixel to form one display element of the liquidcrystal element apparatus, and each second electrode comprises atransparent conductive electrode formed to overlap the first electrodethrough an insulating film and including an area smaller than an area ofthe first electrode, to generate the horizontal electric field betweenthe first electrode and an edge of the second electrode which overlapsthe first electrode. In this case, preferably, each second electrodecomprises a comb-shaped conductive film formed on the first substrateand patterned into a comb shape having a plurality of electrode fingerportions extending in one direction. Also, desirably, the electrodefinger portions of the comb-shaped conductive film extend in a directionintersecting the direction of aligning treatment of the liquid crystaldisplay apparatus.

Preferably, this liquid crystal display apparatus further comprises adisplay driver to supply a voltage to generate an alignment transitionelectric field to the first, second, and third electrodes at a start ofthe liquid crystal display apparatus, the alignment transition electricfield comprising a vertical electric field in a thickness direction ofthe liquid crystal layer and a horizontal electric field in a directionparallel to the inner surfaces of the first and second substrates and totwist the liquid crystal molecules between the substrates, and to causethe liquid crystal molecules to transit from splay alignment to bendalignment. In this case, desirably, the display driver supplies avoltage to generate the vertical electric field to at least the secondand third electrodes, and a voltage to generate the horizontal electricfield to the first and second electrodes. The liquid crystal displayapparatus further desirably comprises a plurality of active elementsconnected to the second electrodes, each active elements being arrangedon the first substrate to correspond to a pixel to form one displayelement of the liquid crystal display apparatus.

Furthermore, a liquid crystal display apparatus according to the presentinvention comprises a liquid crystal layer sealed between a firstsubstrate and a second substrate opposed to each other, inner surfacesof the first and second substrates having been subjected to aligningtreatment to align liquid crystal molecules of the liquid crystal layerin a splay configuration, a plurality of pixel electrodes formed on theinner surface of the first substrate, a plurality of auxiliaryelectrodes which are formed on the inner surface of the first substrateto be insulated from the pixel electrodes to generate, with respect tothe pixel electrodes, a horizontal electric field to twist the liquidcrystal molecules of an intermediate layer, excluding liquid crystalmolecules of the liquid crystal layer which are adjacent to the innersurfaces of the first and second substrates, within a plane parallel tothe inner surfaces of the first and second substrates, and acounterelectrode, formed on the inner surface of the second substrate tooppose at least the pixel electrodes, to generate a vertical electricfield in the thickness direction of the liquid crystal layer withrespect to the pixel electrodes.

In this liquid crystal display apparatus, preferably, each auxiliaryelectrode comprises a conductive film with an area corresponding to thea pixel to form one display element of the liquid crystal displayapparatus, and each pixel electrode comprises a comb-shaped conductivefilm which is formed on the first substrate to overlap the auxiliaryelectrode through an insulating film and patterned into a comb shapeincluding electrode finger portions extending in one direction togenerate the horizontal electric field between the auxiliary electrodeand edges of the electrode come portions. In this case, desirably, theliquid crystal display apparatus further comprises a display driver tosupply a voltage to generate an alignment transition electric fieldcomprising the horizontal electric field and the vertical electric fieldto the auxiliary electrodes, pixel electrodes, and counterelectrode whenstarting the liquid crystal display apparatus, and a voltage to generatean electric field corresponding to image data in the thickness directionof the liquid crystal layer to at least the pixel electrodes andcounterelectrode after the liquid crystal display apparatus is started.Desirably, the display driver supplies a voltage to generate thevertical electric field to the pixel electrodes and counterelectrode,and a voltage to generate the horizontal electric field to the auxiliaryelectrodes and the pixel electrodes. The liquid crystal displayapparatus further desirably comprises thin film transistors connected tothe pixel electrodes, each pixel electrode being arranged on the firstsubstrate to correspond to a pixel to form one display element of theliquid crystal display apparatus.

According to the above embodiment, of the first and second electrodes 4and 5 which generate the horizontal electric field to twist the liquidcrystal molecules 3 a at the start, the first electrodes 4 are formed tocorrespond to at least the entire area of the pixels 110, and the secondelectrodes 5 are formed of the comb-shaped conductive films 5 a on theinterlayer dielectric film 14 which covers the first electrodes 4.However, the present invention is not limited to this. The first andsecond electrodes 4 and 5 may comprise first and second comb-shapedconductive films having opposite patterns. The electrode finger portionsof one of the first and second electrodes 4 and 5 and those of theremaining electrodes may be adjacent to each other via gaps along thesurface of the rear substrate 1. In this case, the first and secondelectrodes respectively comprising the first and second comb-shapedconductive films are arranged to correspond to the pixels 110. Thealignment transition electric field is generated between the first andsecond electrodes and the third electrode 15 formed on the remainingsubstrate 2.

According to the above embodiment, the electrodes 4 and 5, whichgenerate a horizontal electric field to twist the liquid crystalmolecules 3 a at the start, are formed on the inner surface of one ofthe substrates 1 and 2. Alternatively, electrodes which generate atransition electric field to twist the liquid crystal molecules 3 a atthe start may be formed on the inner surfaces of both of the substrates1 and 2.

Furthermore, according to the above embodiment, the vertical electricfield is applied between the second electrodes 5 and third electrode 15,and the horizontal electric field is applied between the firstelectrodes 4 and second electrodes 5, to apply the electric field thatforms the bend alignment state at the start. In the display drivingstate after this, the first electrodes 4 and second electrodes 5 may beset at the same potential. Alternatively, a display signal correspondingto the image data may be supplied to both of the first electrodes 4 andsecond electrodes 5. An electric field corresponding to the image datamay be applied to the liquid crystal layer between the first and secondelectrodes 4 and 5 and the third electrode 15.

Additional advantages and modifications will readily occur to thoseskilled in the art. Therefore, the invention in its broader aspects isnot limited to the specific details and representative embodiments shownand described herein. Accordingly, various modifications may be madewithout departing from the spirit or scope of the general inventiveconcept as defined by the appended claims and their equivalents.

What is claimed is:
 1. An alignment transition method for causing liquidcrystal molecules in a liquid crystal layer to transit from splayalignment to bend alignment, the liquid crystal layer being providedbetween a first electrode and a second electrode, the method comprising:forming a plurality of slits extending in parallel with each other inthe second electrode and providing a third electrode disposed to coverthe plurality of slits through an insulating film, the third electrodebeing provided such that the insulating film is interposed between thethird electrode and the liquid crystal layer; and causing, when theliquid crystal molecules in the liquid crystal layer exhibit the splayalignment, the liquid crystal molecules to transit from the splayalignment to the bend alignment by applying voltage between the firstelectrode and the second electrode while applying voltage between thesecond electrode and the third electrode, wherein the liquid crystalmolecules are nematic liquid crystals having positive dielectricanisotropy wherein the plurality of slits are formed to extend in adirection slanting at a predetermined angle with respect to an alignmentdirection of the liquid crystal molecules which exhibit the splayalignment; wherein the predetermined angle is in a range from 5° to150°.
 2. The method according to claim 1, wherein the plurality of slitsare formed in an area corresponding to one pixel.
 3. The methodaccording to claim 1, wherein intervals between adjacent slits of theplurality of slits are equivalent.
 4. The method according to claim 1,wherein the first electrode and the second electrode are provided indifferent substrates.